438 Systematic Paleontology 



at least of the Wealden twigs identified as 8pJienolepis Sternbergiana 

 may really be those of Sequoia ambigua, which in this country we have 

 no difficulty in distinguishing from Sphenolepis. 



Occurrence. — Patuxent Formation. Fredericksburg, Telegraph 

 Station (Lorton), Potomac Eun, Alum Eock, Cockpit Point, Wood- 

 bridge, Virginia. Arundel Formation. Langdon, District of Colum- 

 bia; Hanover, Tip Top, Soper Hall, Maryland. Patapsgo Formation. 

 Grays Hill, Ft. Foote, Stump Neck, Maryland; Mt. Vernon, White 

 House Bluff, Hell Hole, Chinkapin Hollow, 72-mile post, Dumfries 

 Landing, near Widewater, Aquia Creek, Virginia. 



OoUections. — U. S. National Museum, Johns Hopkins University. 



Genus ARTHROTAXOPSIS Fontaine 

 [Mon. U. S. Geol. Survey, vol. xv, 1890, p. 239] 



The genus Arth^'otaxopsis naTaed from its resemblance to the modern 

 genus Artlirotaxis Don of the subfamily Taxodiese which has three 

 species confined to Tasmania, is characterized in the following terms by 

 its describer: 



" Trees or shrubs, copiously branching, with principal stems or 

 branches proportionally strong, cylindrical, rigid, sending ofi; thickly 

 placed, long, slender, cord-like, ultimate twigs, all in the same plane 

 and spreading widely; the ultimate twigs leave the penultimate ones 

 under a very acute angle and show a tendency to a fastigiate grouping; 

 cones mostly broadly oblong, rarely globular, obtuse and rounded at 

 base and apex, average dimensions 10 mm. by 14 mm. attached singly 

 on the summit of short lateral branches and placed on the lower 

 portions of the leafy stems and branches, the twig with its cone repre- 

 senting the branching leafy twigs which occur higher up; scales of the 

 cones woody, thick, wedge-shaped in the basal portions, expanded at the 

 free ends, and probably shield-shaped, numerous, spirally placed, attached 

 at a large angle, the middle ones being nearly or quite at a right angle 

 with the axis, close appressed, opening with age; seed under each scale 

 one, elliptical in shape, smooth and bony in texture, average dimensions 

 1 mm. by 2.5 mm; leafy branches ending abruptly in an ultimate twig 



